This invention relates to apparatus for conveying finely divided material of the fluidizing gravity conveyer type and is particularly designed for conveying high temperature material including material in excess of 500.degree. F.
Prior to the present invention, it was known to utilize conveying apparatus for finely divided material such as alumina, cement raw meal, finish cement and the like, wherein a conveying conduit includes a gas permeable member dividing the conduit into an upper material chamber and a lower plenum chamber. The conduit includes an inlet at one end for supplying material to be conveyed to the material chamber and an outlet end for discharging material from the conduit. Gaseous fluid under pressure, such as air, is supplied to the lower plenum chamber for passage upwardly through the gas permeable member. Material supported on the gas permeable member in the material chamber is aerated and fluidized by the air under pressure. When fluidized, the material will flow downwardly from the inlet to the outlet by gravity. Usually, the conveying apparatus is set at a small slope such as 6.degree. to facilitate material flow. Typical apparatus of this type are shown in U.S. Pat. No. 2,527,488.
Fluidizing gravity conveyers presently in use utilize tightly woven fabric with closely controlled air porosity as the gas permeable member. Prior to the present invention it was also known to utilize porous stones and sintered metals in place of the woven fabric for higher temperature applications. With a fabric gas permeable member. if high temperature materials are to be conveyed, the fabric will ignite and destroy the apparatus. The porous stones and sintered metals were capable of handling higher temperatures, but not the temperatures required for various applications such as in conveying very hot material.
It would be advantageous to be able to convey finely powered material at high temperatures such as temperatures on the order of 1000.degree. to 1600.degree. F. One such application would be in a preheater utilized in the cement manufacturing process. In such a process, high temperature gases exhausted from the rotary kiln utilized to produce the cement clinker are utilized to preheat raw material being supplied to the clinkering furnace. Typically, there preheaters consist of a plurality of serially connected cyclone separators with material being alternately entrained in the hot gases and separated by the cyclones to thereby preheat the material to as much as 1500.degree. or 1600.degree. F. A typical application is shown in U.S. Pat. application Ser. No. 883420 filed July 8, 1986 assigned to the assignee of the present application. Another application of fluidizing gravity conveyers in cement preheaters is shown in Japanese Patent Pre-Publication No. 58-156187, published Sept. 17, 1983.